Test toggle states with RSpec

https://dev.to/satish/using-feature-flags-aka-feature-toggles-in-microservices-and-devops-13oh

Feature toggles are commonly used while developing new features in existing applications. It’s the best alternative to branch-based development.

Feature toggles can be stored along with application code or you can store them separately and use them across services and update them without deploying your application changes. Below are examples of them:

Storing feature toggle in a separate service and accessing those:

require 'httparty_patch'

class ToggleApi
  include HTTParty

  base_uri TOGGLE_API_URL

  class << self
    def on? name
      put("/read?name=#{name}", headers: {'Content-Type': 'application/json'})
    end
  end
end

ToggleApi.on?('new_tax_scheme')

Storing toggles in application code:

class Toggle
  def self.on?(name)
    toggles[name]
  end

  private

  def self.toggles
    {
        'new_tax_scheme' => true,
        'increase_gst' => false
    }
  end
end

You can choose to achieve it in different ways. We will use the above sample code for reference.

I have created a class where based on toggle we are finding if income is taxable.

class Income < ApplicationRecord
  def taxable?
    if Toggle.on?('new_tax_scheme')
      amount > 500000
    else
      amount > 250000
    end
  end
end

To test this behaviour we can stub toggle values to test the behaviour of both states.

require 'rails_helper'

RSpec.describe Income, type: :model do
  describe '#eligible_for_tax?' do
    context 'when new_tax_scheme toggled on' do

      before do
        allow(Toggle).to receive(:on?).with('new_tax_scheme').and_return(true)
      end

      it 'should return true if amount is more than 5L' do
        income = Income.new(amount: 600000)
        expect(income.taxable?).to be_truthy
      end

      it 'should return false if amount is less than 5L' do
        income = Income.new(amount: 400000)
        expect(income.taxable?).to be_falsy
      end
    end

    context 'when new_tax_scheme toggled off' do

      before do
        allow(Toggle).to receive(:on?).with('new_tax_scheme').and_return(false)
      end

      it 'should return true if amount is more than 2.5L' do
        income = Income.new(amount: 400000)
        expect(income.taxable?).to be_truthy
      end

      it 'should return false if amount is less than 2.5L' do
        income = Income.new(amount: 100000)
        expect(income.taxable?).to be_falsy
      end
    end
  end
end

If you are maintaining toggles in a separate service you can stub toggle state in a similar way.

allow(ToggleApi).to receive(:on?).with('new_tax_scheme').and_return(false)

Happy Testing!!!